This invention relates to the transportation of heavy equipment by airplanes, and in particular to the transportation of wheeled or track laying vehicles.
There is an increasing need for such transportation to support construction work in remote and/or inaccessible areas and for military purposes. Furthermore, in times of war or other emergencies there may be an urgent need to increase the capability for such transport as rapidly and economically as possible. Further, particularly for war time use, it would be necessary that the loading and unloading of the vehicles involve minimum of complication of equipment and procedures and a minimum of ancillary equipment. Rapid increase in capability could involve converting passenger aircraft to transports capable of carrying vehicles and it would be vital that the conversion be made as quickly and economically as possible. Such conversions would involve installing cargo doors in the sides of the airplanes and, for structural and economic reasons, it would be important that the door size be kept as small as possible relative to the maximum size vehicles which can fit into the body of the airplanes. Also, in aircraft with door size already established, it is important to accommodate as great a vehicle length as possible in order to optimize the utility of the aircraft.
Increased capability can also be provided by utilizing airplanes designed primarily as tankers for refuelling other aircraft. In tanker airplanes the full payload of fuel can be carried below the floor. Thus the volume above the floor is available to carry cargo when the airplanes are not needed for their primary purpose or for both purposes when circumstances so dictate. In this instance it is important that the adaptation of the airplane to serve the secondary purpose of carrying cargo involves a minimum of added cost and weight. Therefore, again, the door should be as small as possible relative to the dimensions of the cargo space and the vehicles to be transported. Also, the apparatus should be simple and economical as explained above.
There are a variety of existing cargo loading methods and apparatus, ranging from highly sophisticated concepts to those which are rudimentary but effective. U.S. Pat. No. 4,050,655, entitled "Cargo Loading Method and Apparatus," issued to Robert E. Bogue, et al., shows an example of a sophisticated concept. One of the advantages of the concept is that cargo units longer than the width of the door or the width of the cargo space can be loaded and unloaded through a side door. This capability meets the above described requirement that door size be as small as possible relative to the dimensions of the cargo compartment and cargo units. However, the complicated nature of the concept makes it too expensive for use in adapting an existing airplane to cargo carrying purposes. Also, the apparatus is designed to work with palletized cargo, and this would impose unacceptable penalties in the transport of wheeled and tracked vehicles. The logistics of having pallets available would be complicated and expensive. Also, the time, effort and personnel requirements to palletize and de-palletize the vehicles would have negative economic influence.
British Pat. No. 876,150, "Improvements In Or Relating To The Conveyance Of Freight Or Other Loads By Aircraft," issued to Thomas M. A. O'Connell, discloses a less sophisticated concept which involves "wheeled load carrying platforms" (pallets) and a turntable. The purpose of the turntable is to enable the platforms to be wheeled through the door into the cargo compartment and then re-aligned 90.degree. to permit movement of the platforms into the fore and aft portions of the cargo compartment. In this concept the cargo components can be no longer than the width of the door or the width of the cargo compartment. Also, wheeled or tracked cargo must be palletized, imposing the economic penalties referred to previously. Furthermore, incorporation of the concept into an existing airplane would require extensive structural modification. Similarly, its incorporation into an airplane designated specifically as an aerial tanker would involve undesirable cost and weight penalties.
Many prior art aircraft designed for carrying wheeled or tracked cargo employ entrance/exit facilities at one or both ends of the cargo compartments. A review of these prior art designs indicate that entrance/exit facilities at the ends of the cargo compartments are, as a practical matter, too complicated to be used in most instances for adapting an airplane to transport wheeled or tracked vehicles.
Therefore, the problem solved by subject invention is the provision of economical and effective adaptation of airplanes to the transportation of wheeled or tracked vehicles. The main purposes of such adaptations are (1) to increase the utility of tanker airplanes with minimum penalty to the performance of the airplane in its basic function; (2) to convert passenger airplanes to carry such cargo in times of emergency and (3) to extend the usefulness of airplanes which are no longer competitive in the field for which they were designed.
It is therefore a primary object of this invention to provide simple and economic adaptation for loading and unloading wheeled or tracked vehicles through a side door of a cargo compartment.
It is a further object, in consonance with the economics of the adaptation, that the door be as small as possible relative to the size of the cargo compartment and the vehicles which will fit into it.
It is a further object also that the apparatus be simple, in regard to its manufacture, installation and operation.